Fix exclude-file-types for known files

[Mak-1911]

PR summary:
Fixes #456

Summary

• Apply --exclude-file-types after resolving file type
• Exclude known files like .gitconfig and justfile by resolved type
• Add regression tests and update docs/test expectations

Test

• go test ./pkg/finder -run "Test_fsFinderExcludeFileTypes|Test_fsFinderKnownFiles|Test_fsFinderLinguistKnownFiles"

Please let me know if there are any further fixes or ammends to make.

[kehoecj]

Thanks for the PR! Code looks good. Testing confirms this change has addressed the issue. A few things before we can merge:

1. Create a changelog entry under [Unreleased] for this bug fix
2. You'll need to generate and commit the new linguist data. I just created #466 so MR authors won't have to do it on future submissions but you'll have to run the below commands to get the job to pass for now:

  go generate ./pkg/filetype/...
  git add pkg/filetype/known_files_gen.go
  git commit -m "chore: regenerate known files from Linguist"

[Mak-1911]

Addressed, thanks.

• Added an Unreleased changelog entry
• Ran go generate ./pkg/filetype/... and committed the regenerated known_files_gen.go.

Let me know if this needs more fixes or additions.